Inhibition of proliferating lens epithelium with antitransferrin receptor immunotoxin.

We investigated the effect of an antitransferrin receptor immunotoxin (454A12-rRA) on proliferating human and baboon lens epithelium in vitro. Human and baboon lens epithelial cells grown in modified TC-199 medium at 35 degrees Celsius in 7% CO2 were seeded in 24 well plates at a density of 17,500 cells/ml to 40,000 cells/ml. The cells were exposed to various concentrations of 454A12-rRA for seven days. The sensitivity of proliferating human lens epithelium to 454A12-rRA was dependent on the dose, with a 60% to 70% reduction in cell counts at immunotoxin concentrations of 100 ng/ml and above. The immunotoxin had no significant effect on baboon lens epithelium in vitro, which suggests that it is specific for human tissue. By preventing the proliferation of human lens epithelial cells, immunotoxin 454A12-rRA may be useful in the management of posterior capsule opacification after planned extracapsular cataract surgery.

Inhibition of human corneal epithelium with immunotoxin 454A12-rRA.

We examined the effects of the immunotoxin 454A12-rRa on proliferating and confluent human corneal epithelium (HCE) in vitro. Proliferating HCE was sensitive to 454A12-rRA in a dose-dependent fashion. At immunotoxin concentrations of 1,000 ng/ml for 7 days we observed an 86% reduction in cell counts. Confluent HCE was not sensitive to 454A12-rRA at equivalent concentrations of immunotoxin. These data confirm previous observations regarding selective sensitivity of proliferating ocular tissue to immunotoxin, but suggest that HCE is less sensitive to 454A12-rRA than other ocular cell types.

Long-term inhibition of cellular proliferation by immunotoxins.

The proliferation and fibrous metaplasia of retinal glial and pigment epithelial cells cause proliferative vitreoretinopathy. The immunotoxin 454A12 MAB-rRA is composed of a murine monoclonal antibody, specific for the human transferrin receptor, and is chemically linked to recombinant ricin A chain, a cellular toxin. The rapidly proliferating cells take up the immunotoxin, but non-proliferating cells do not. Using a collagen-gel medium to simulate the vitreous, we have studied the effect of the immunotoxin on fibroblast proliferation in vitro. Exposure of the fibroblasts to 1000 ng of immunotoxin per milliliter of the collagen gel medium for 10 minutes kills 96% or more of the cells for 20 days. These in vitro data indicate that the immunotoxin is effective in an environment similar to the vitreous; however, in vivo studies will be necessary to prove if it is a suitable agent for the long-term prevention of cell proliferation in the human eye.

A computerized recall system for clinical trials.

A major difficulty facing investigators involved in clinical studies is ensuring the timely follow-up of patients involved in the investigations. Two microcomputer programs are described that create a follow-up calendar for each subject, list patients due to appear for any given month, and generate printouts of subjects who have missed key follow-up appointments. These programs were formulated using dBASE II (Ashton Tate, California), a widely used data base management package suitable for International Business Machines-compatible microcomputers. The programming concept used in formulating these programs can be adapted to most other data base management software systems. These programs are currently enhancing the follow-up of patients enrolled in a prospective ophthalmic surgical protocol and are potentially useful to any investigator involved in prospective studies who has access to a microcomputer.